Embodiments of the disclosed technology relate to a mask plate, a patterning method, and a method for manufacturing an array substrate.
A double-tone mask plate (e.g., a gray scale mask plate or a translucent mask plate) can be used in the process of manufacturing the array substrate of a horizontal electric field type thin film transistor liquid crystal display (TFT-LCD). Such a mask plate may comprise three regions, i.e., a transparent region, a light-blocking region and a translucent region. After exposing of photoresist (e.g., positive photoresist) with the mask plate, an exposed region is formed in the photoresist layer corresponding to the transparent region of the mask plate; an non-exposed region is formed in the photoresist layer corresponding to the light-blocking region of the mask plate; and an half-exposed region is formed in the photoresist layer corresponding to the translucent region of the mask plate. After development of the exposed photoresist, the photoresist in the exposed region and a portion of the photoresist in the half-exposed region is removed.
Since the desired patterns (e.g., conductive lines or via holes) in the half-exposed region are formed on the substrate after two subsequent etching processes are performed, the thickness and uniformity of the remaining photoresist in the half-exposed region should be strictly controlled. If the thickness of the remaining photoresist is too big, the time of the subsequent etching will be prolonged. If the thickness is too small, the peripheral morphology of the photoresist will be deteriorated and even a totally uncovered region will occur instead. One of the most important factors affecting the thickness of the remaining photoresist in the half-exposed region is the developer concentration of development solution. During development, the development solution applied to the photoresist reacts with the photoresist to be removed. The amount of the photoresist that is removed within a certain period of time increases with the developer concentration.
Generally, a five-mask process may be used to fabricate the array substrate of a horizontal electric field type TFT-LCD. Specifically, a first mask plate is used to form the patterns of a first transparent common electrode layer; a second mask plate is used to form the patterns of a gate metal layer; a third double-tone mask plate is used to form the patterns of a semiconductor active layer and a source/drain metal electrode layer; a fourth mask plate is used to form the patterns a via hole layer; and a fifth mask plate is used to form a pixel electrode layer. Currently. the first transparent pixel electrode layer and the gate metal layer can be patterned by using a same double-tone mask plate so as to save cost and reduce the amount of the mask processes.